Beverages such as milk, juice and the like are provided with, for example, gable-top containers. Beverages packed by the container are exposed to sunlight and lighting of fluorescent lamp of a refrigeration showcase in distribution processes for long time.
As for a photosensory food such as low-fat cow's milk, certain of consumers recognize that some off-flavor is generated in the food of cow's milk by the effect of the light.
Therefore, the paper packaging material/the packing container/the cup which have a light barrier is drawn attention of, and various materials have been suggested and used.
The following proposals are mentioned: for example, a packaging material having a light barrier layer between a substrate and an innermost layer and a coloring printing layer on one side thereof (JP A 7-52328), a cup including a barrier film, a light barrier layer, a cover-up layer in a paper substrate (JP A 11-130044), a laminate having a paper substrate layer, a metal vapor deposition plastic interlayer and a metallocene polyethylene internal layer (JP A 09-86537), a packaging material provided with a light barrier layer comprising gel-like synthetic resin, light barrier agent and wax on at least one surface of a paper support (WO A 0175227), a paper-made liquid container with a paper layer, a transparent gas barrier layer, a coloring light barrier layer and a thermoplastic resin layer (JP A 06-238834), a paper laminated material with a cardboard substrate, a light barrier resin layer, a white resin layer and an innermost layer (JP A 09-24583), a packaging material comprising a paper layer, an outside polyolefin resin layer, a barrier layer, an inside polyolefin seal layer and a light barrier materials between any of their layers (JP A 06-135439).
However, the above-mentioned proposals mostly provide the light barrier layer in the inside of the paper substrate. When the food such as cow's milk being sensitive to chemical is filled up, from viewpoint of legal regulation and effect to taste, it is unfavorable to provide the light barrier layer in the food side.
In a method, a light barrier layer is printed with black ink to a paper substrate, and the effect of the black ink is shielded with a clay coat layer by a clay coater In the method, a packaging material having a layer structure comprising an outside laminate layer/a design printing layer/a clay court layer/a light barrier layer of black ink/a paper substrate/an inside laminate layer is obtained.
However, the method includes many total manufacturing steps with very high costs. Because the black ink is printed directly on the paper layer, the black ink penetrates through the paper fiber, and an ink removing apparatus is necessary for reproduction in the recycle.
In other packaging material with a layer structure comprising a printing layer of design/a white ink layer/a white ink layer/a white ink layer/a black ink layer/a laminate layer/a paper substrate/an outside laminate layer, a few colors white inks are used to shield the effect of the black ink after the extrusion laminate. However, most packaging materials for gable-top containers is purchased as the so-called poly-coat paper which is laminated, are converted in a packaging material factory. When three or four colors white inks are used in the converting steps, the remaining color number for the press becomes short, and the design is limited. In addition, as a result, the number of the laminated ink becomes six or seven colors, and the ink layers might be de-laminated.